The influences of carbon sources, fructose, glucose, sorbitol and sucrose on shoot proliferation and in vitro rooting
of cork oak (Quercus suber L.) were compared at a wide range of concentrations (1-6%, w/v). The highest number
of shoots occurred on glucose-containing medium. Nevertheless, we have chosen 3% sucrose which induced a
similar rate of proliferation but favoured shoot elongation, permitting an effectively higher number of shoots during
transfers. Sorbitol and autoclaved fructose did not stimulate shoot proliferation. Adventitious root formation was
strongly dependent on carbohydrate supply. Sorbitol and autoclaved fructose were completely ineffectively on
rooting induction. Glucose was the most effective carbon source on rooting promotion followed by sucrose and
filter-sterilized fructose. The rooting response induced by fructose was dependent on the sterilizing procedure. The
number of adventitious roots produced per shoot increased with increasing glucose and sucrose concentration. The
content of reducing sugars in leaves of proliferation cultures and in leaves and roots of rooted plantlets was more
dependent on carbon concentration than on glucose or sucrose supplement. The results presented here show that
carbohydrate requirements during cork oak micropropagation depend upon the phase of culture. Sucrose (3%) and
glucose (4%) were the best carbon sources respectively during proliferation and rooting phases.